Lignocellulosic biomass is viewed as an abundant renewable resource for fuels and chemicals due to the presence of sugars in the cell walls of plants. More than 50% of the organic carbon on the earth's surface is contained in plants. This lignocellulosic biomass is comprised of hemicelluloses, cellulose and smaller portions of lignin and protein. Cellulose is a polymer comprised mostly of condensation polymerized glucose and hemicellulose is a precursor to pentose sugars, mostly xylose. These sugars can easily be converted into fuels and valuable components, provided they can be liberated from the cell walls and polymers that contain them. However, plant cell walls have evolved considerable resistance to microbial, mechanical or chemical breakdown to yield component sugars. A number of approaches to overcome this recalcitrance have been performed and the breakdown of these polymers into sugars, saccharification, has a long history. During such breakdown and/or saccharification, monomeric and oligomeric pentoses contained in the cell walls are released and can be subjected to acid-catalyzed dehydration to provide furfural, an important bio-based intermediate in the manufacture of fuel and chemicals, as reviewed by J. P. Lange, E. van der Heide, J. van Buijtenen, R. J. Price, ChemSusChem 2012, 5, 150-166.
US 20140018555 describes a process for producing furfural from lignocellulose-comprising biomass is disclosed. The biomass is slurried in water and optionally an acid, subjected to hydrolysis, and then subjected to a solid/liquid separation to yield at least an aqueous fraction comprising C5 and C6 sugars and a solid fraction comprising cellulose and lignin. Furfural is obtained by adding an organic solvent to the aqueous fraction, heating at 120-220° C. for a sufficient time to form furfural, cooling, and separating an organic phase comprising at least part of the furfural from an aqueous phase. As suitable organic solvents water miscible and water immiscible organic solvents are suggested. However, the process of US 20140018555 requires a continuous supply of organic solvent, which is undesired when the process is operated at remote locations. There is a need for improving the efficiency of the process by reducing the demand for organic solvent to be provided to the process.
Dumesic et al, (Elif I. Gurbuz, Stephanie G. Wettstein, and James A. Dumesic, Conversion of Hemicellulose to Furfural and Levulinic Acid using Biphasic Reactors with Alkylphenol Solvents, ChemSusChem 2012, 385-387) reported the acid-catalysed dehydration of xylose to furfural using a bi-phasic medium based on water and lignin-derived solvent (LDS). The LDS was shown to be a powerful extractant for furfural and can be made from the lignocellulose, avoiding thereby the need for external solvent. In Dumesic, the lignin-derived solvent (LDS) was derived from poplar wood using hot-compressed water under moderate hydrogen pressure utilizing a metal catalyst, followed by extraction from the aqueous phase using diethyl ether (DEE) to obtain a mixture of propyl guaiacol (PG), propyl syringol (PS), guaiacyl propanol and syringyl propanol. The final LDS mixture was obtained by evaporating the DEE solvent, followed by the removal of guaiacyl propanol and syringyl propanol from the mixture by extraction with water, leaving a hydrophobic organic phase composed of PS and PG in a 4:1 mass ratio. This process taught by Dumesic requires the use of solid precious metal catalyst in the presence of solid biomass to produce the LDS component. As such, the process taught by Dumesic is complex and expensive to separate the metal catalyst from solid biomass after the reaction. Also, the impurities in biomass may shorten the life of the catalyst in Dumesic. Further, in Dumesic, the LDS component needs to be further extracted via solvent leading to complex separations to produce the LDS component for use in the reaction for furfural production. In contrast, the presently disclosed subject matter provides for separation of the lignin from the pre-treated biomass by solvent treatment without the need for any solid metal catalyst, thereby simplifying the process steps to produce phenolic solvent components.